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Home , Azufral, Cerro Bravo, Chiles (volcano), Cundinamarca Department, Duitama, Galeras

Proceedings World Geothermal Congress 2005 Antalya, Turkey, 24-29 April 2005

Colombian Geothermal Resources

Claudia Alfaro*1, Francisco Velandia*2 and Héctor Cepeda*3 * INGEOMINAS. Dg. 53 No. 34-53. , 1 [email protected] , 2 [email protected], 3 [email protected]

Keywords: Colombia, , , , electromagnetic surveys and geochemistry of the aqueous structural geology of Paipa, vulcanism at the Eastern phase of the hot springs. From them a high temperature Cordillera, geochemistry of hot springs. geothermal system is proposed with a magmatic heat source, an upflow controlled by deep faults and a shallow ABSTRACT mixing process with a highly sodium mineralized water which “masks” the chemical composition of the deep During the last few years, new legal dispositions have reservoir fluid. favored the promotion of non-conventional energy sources in Colombia: The law 697 of 2001 declared the rational and efficient use of energy and the utilization of non- 1. INTRODUCTION conventional energy sources, as a social and public interest Between 2000 and 2005, new legal dispositions have matter as well as a national convenience issue. The same favored the promotion of non-conventional energy sources law, demands stimulus for developing non-conventional in Colombia. The law 697 of 2001 declared the rational and energy sources from the government. The edict 3683 dated efficient use of energy and the utilization of non- December 2003, regulates the promotion of non- conventional energy sources, as a social and public interest conventional energy sources, inside the frame of sustainable matter as well as a national convenience issue. The same development, following the recommendations of The law, demands encouragement for developing non- Johannesburg Summit, in which Colombia participated. conventional energy sources from the government. The edict 3683 dated December 19, 2003, regulates the Since 2000 the geothermal project of INGEOMINAS which promotion of non-conventional energy sources, inside the is the institution in charge of the geothermal exploration in frame of sustainable development, following the Colombia, have worked on two topics: 1) The inventory of recommendations of The Johannesburg Summit. hot springs, in two areas: – Cerro Machín Volcanic Complex and and 2) INGEOMINAS is the governmental institution in charge of the first stage of exploration two areas: Azufral the geothermal exploration in Colombia. During the last () Paipa geothermal area (Boyacá five years this institution carried out studies of inventory of Department). hot springs at the geothermal areas of Cerro Bravo – Cerro Machín Volcanic Complex and Cundinamarca department The inventory of hot springs at Cerro Bravo – Cerro and the first stage of geothermal exploration at the Machín Volcanic Complex was based in the reinterpretation geothermal areas of Azufral Volcano and Paipa, which are of the geochemical existing information. The Santa Rosa de indicated in the Fig. 1. Cabal group, constituted by the springs of San Vicente and Santa Rosa sectors, revealed the highest interest as an 2. GEOTHERMAL STUDIES BACKGROUND energy resource given the highest geochemical temperatures inferred in the reservoir. This is proposed as The geothermal anomaly hosted in the Colombian territory an independent system from Nevado del Ruiz. related to the zone is related in turn with several hydrothermal systems located mainly around the volcanoes The inventory of hot springs from Cundinamarca of the Andean Cordillera. The main identified geothermal department indicate the existence of this surface areas are the Cerro Bravo - Cerro Machín Volcanic manifestatons at 27 municipalities, from which 52 mineral Complex, the volcanoes from the south of the Country at and hot springs were characterized. The spatial distribution Nariño Department (Azufral, , Cumbal, of the springs shows a trend to increase their temperature volcanoes) and the Paipa – Iza sector, in Boyacá towards the East of the Department, reaching a maximum Department. A summary of the reconnaissance and of 73.6°C at locality. From the geochemistry prefeasibility studies, as well as the first version of the of the springs, Cundinamarca has geothermal resources of geothermal map was presented in the frame of the WGC low temperature related to a normal geothermal gradient. 2000 (Alfaro et al., 2000).

The first stage of exploration at Azufral volcano included 3. UTILIZATION the preparation of the geological cartography of the area as The geothermal resources utilization is restricted in well as the updating of the chemical composition of hot Colombia to bathing and swimming with recreational springs. The stratigraphy of Quaternary deposits together purposes, mainly. However the local communities, where with a geochronological study allowed defining a new the hot springs are located, recognize their healing geological formation. The geochemistry of the springs properties. Currently, as result of the wide access to the shows a probable contribution of a saline non geothermal information, the development of the medical balneology source. The quartz geothermometers indicate a minimum and thermalism in many countries, particularly in Europe, is probable temperature of 180°C. object of an increasing interest in

At Paipa geothermal area the work included geological studies of cartography, tectonics and volcanological,

1 Alfaro et al.

and mud flows, product from the volcanic activity of the Quaternary.

The Quaternary deposits from Cerro Bravo to Cerro Machín are predominantly andesitic rocks with variations from rhyodacites to (Cerro Bravo, Nevado del Ruiz, Cerro Bravo – Cerro Machín Páramo de Santa Rosa and Machín) to basaltic Volcanic complex from Nevado del Quindio and , product Paipa geothermal of the and activity. area

Cundinamarca The tectonic setting of the area is defined by the systems of Department faults , Palestina and Mulato with NNE-SSW Azufral volcano direction (Geocónsul, 1992). The Romeral , which divides the oceanic crust towards the west and, the continental crust to the east, represents and old subduction zone (Barrero et al., 1969, in Calvache & Monsalve, 1982). The compressive forces result in the uplift of the Cordillera Central and the formation of fault systems such as Mulato, Palestina, Marulanda, Salamina and Salento. has been an important conduct for the more ancient Figure 1. Location of the geothermal areas studied in emissions for the volcanoes of the Complex (CHEC et al., the last five year. Two types of studies were 1983). Local faults related to Romeral and Palestina, carried out: Inventory of hot springs identified at represent distensive strength due to the existence of dacitic blue areas and first stage of exploration activities dikes related to them. The current manifestation of these at red areas. faults is the volcanotectonic seismicity associated to the formation of fumarolic fields (Nereidas y La Olleta) and to Colombia, which is reflected in the creation of the the occurrence of hot springs (Calvache & Monsalve, Colombian Hydrothermal Techniques Association in 1998 1982). with the participation of the tourism sector as well as INGEOMINAS, as the governmental institution for 3.1.1.2 Hot Springs technical support, which after the recent reorganization From the spatial distribution and the probable association to keeps its mission of exploring the geothermal resources. specific volcanoes, the total of 100 springs, from which 74 Additionally, the agreement between the governments of can be considered thermal, were divided in nine (9) groups Rumania and Colombia was approved through the Law 595 presented in Fig. 2: (1) Cerro Bravo volcano, (2) Nevado of 2000, for the cooperation in tourism in particular to del Ruiz -eastern sector, (3) Batolito El Bosque, (4) Nevado promote the social tourism, health tourism, hydrothermal del Ruiz – western sector, (5) Santo Domingo, (6) Santa treatments, between others. The list of localities with hot Rosa, (7) El Bosque del Otún, (8) Nevado del Tolima and springs utilization in bathing and swimming is presented in (9) Cerro Machín volcano (Alfaro et al., 2002). Table 1, together with the estimation of the thermal energy utilization. In the localities of Paipa and Santa Rosa de A high diversity of chemical compositions is found in these Cabal, a more systematic use of these resources has been springs including those compatible with a significant implemented with programs for relaxation and health volcanic-magmatic fluid contribution (high temperature, tourism. high sulphate and chloride concentrations and very low pH), in the group 2. On the other hand, deep mature water 3. GEOTHERMAL RESOURCES AND POTENTIAL contribution is inferred, mainly, in the groups 1, 4, 6 and 9. In Colombia the geothermal resources are still an object of The group 1 located at the north of the Cerro Bravo volcano preliminary exploration and there are not significant is formed by 12 neutral bicarbonate springs around Cerro utilization developments. A description of exploration Bravo volcano. Their chemical composition indicates the studies carried out during the last five years is presented deep water contribution. The estimated reservoir next. temperature, based on the silica geothermometers points out 3.1 Inventory of Hot Springs up to 156°C. 3.1.1 Cerro Bravo – Cerro Machín Volcanic Complex. The group 4, Nevado del Ruiz-western sector, was chosen The Cerro Bravo – Cerro Machín volcanic complex is as one of the highest priority areas for the geothermal located along the Central Cordillera between Caldas, exploration (CHEC et al., 1983). It is formed by 10 springs, Risaralda, Quindío and Tolima departments, with an rough from which 5 are neutral chloride, exhibit high lithium and 2 area of 2.000 km , which the Parque Natural de los boron contents, up to 3.5 and 17.3 mg/, respectively and Nevados and the volcanoes Cerro Bravo and Cerro Machín. reaches one of the highest discharge temperatures (93°C at Botero Londoño spring). The highest geochemical 3.1.1.1 Geological Setting. temperatures indicate 255°C and 177°C for the Na/K and In general the stratigraphy of the area consists of a quartz geothermometers, respectively. Paleozoic polymethamorphic (Cajamarca group) covered by massive lava flows from the early volcanic The group 6 consists of 15 springs located to the east of the structures of the Cordillera Central of age, which municipality of Santa Rosa and distribute in two sectors: are overlayed by deposits of pyroclastic flows, lava flows San Vicente and Santa Rosa. The highest discharge temperature

2 Alfaro et al.

TABLE 1. UTILIZATION OF GEOTHERMAL ENERGY FOR DIRECT HEAT IN COLOMBIA AS OF 31 DECEMBER 2004 (other than heat pumps)

1) I = Industrial process heat H = Individual space heating (other than heat pumps) C = Air conditioning (cooling) D = District heating (other than heat pumps) A = Agricultural drying (grain, fruit, vegetables) B = Bathing and swimming (including balneology) F = Fish farming G = Greenhouse and soil heating K = Animal farming O = Other (please specify by footnote) S = Snow melting

2) Enthalpy information is given only if there is steam or two-phase flow

3) Capacity (MWt) = Max. flow rate (kg/s)[inlet temp. (oC) - outlet temp. (oC)] x 0.004184 (MW = 106 W) or = Max. flow rate (kg/s)[inlet enthalpy (kJ/kg) - outlet enthalpy (kJ/kg)] x 0.001

4) Energy use (TJ/yr) = Ave. flow rate (kg/s) x [inlet temp. (oC) - outlet temp. (oC)] x 0.1319 (TJ = 1012 J) or = Ave. flow rate (kg/s) x [inlet enthalpy (kJ/kg) - outlet enthalpy (kJ/kg)] x 0.03154

5) Capacity factor = [Annual Energy Use (TJ/yr)/Capacity (MWt)] x 0.03171 Note: the capacity factor must be less than or equal to 1.00 and is usually less, since projects do not operate at 100% of capacity all year.

Note: please report all numbers to three significant figures.

Maximum Utilization Capacity3) Annual Utilization Locality Type1) Flow Rate Temperature (oC) Enthalpy2) (kJ/kg) Ave. Flow Energy4) Capacity 5) (kg/s) Inlet Outlet Inlet Outlet (MWt) (kg/s) (TJ/yr) Factor B 10,2 36,2 28,0 0,35 6,47 7,00 0,63 Agua de Dios B 10,2 36,2 28,0 0,35 6,47 7,00 0,63 Bochalema B 3,49 57,0 33,0 0,35 2,21 7,00 0,63 Cumbal (Chiles) B 10,5 41,0 33,0 0,35 6,63 7,00 0,63 Chinácota B 6,43 46,0 33,0 0,35 4,08 7,00 0,63 Choachí B 12,0 35,0 28,0 0,35 7,58 7,00 0,63 Choachí B 4,86 50,2 33,0 0,35 3,09 7,00 0,63 Chocontá B 6,11 46,7 33,0 0,35 3,87 7,00 0,63 Chocontá B 3,31 58,3 33,0 0,35 2,10 7,00 0,63 Coconuco B 3,35 58,0 33,0 0,35 2,12 7,00 0,63 Coconuco B 2,04 74,0 33,0 0,35 1,29 7,00 0,63 Colón B 5,98 47,0 33,0 0,35 3,79 7,00 0,63 Cuítiva (El Batán) B 3,64 56,0 33,0 0,35 2,31 7,00 0,63 Gachetá B 2,47 66,9 33,0 0,35 1,57 7,00 0,63 Gachetá B 3,36 57,9 33,0 0,35 2,13 7,00 0,63 B 11,3 35,4 28,0 0,35 7,17 7,00 0,63 Güican B 8,37 38,0 28,0 0,35 5,31 7,00 0,63 Ibagué B 5,58 48,0 33,0 0,35 3,54 7,00 0,63 Iza B 5,23 49,0 33,0 0,35 3,32 7,00 0,63 Iza B 4,40 52,0 33,0 0,35 2,79 7,00 0,63 La Calera B 16,7 33,0 28,0 0,35 10,61 7,00 0,63 B 4,92 50,0 33,0 0,35 3,12 7,00 0,63 Nemocón B 14,7 33,7 28,0 0,35 9,31 7,00 0,63 Paipa B 3,64 56,0 33,0 0,35 2,31 7,00 0,63 Paipa B 2,26 70,0 33,0 0,35 1,43 7,00 0,63 Paratebueno B 2,06 73,7 33,0 0,35 1,30 7,00 0,63 Puracé B 12,0 32,0 25,0 0,35 7,58 7,00 0,63 Ricaurte B 17,4 31,8 27,0 0,35 11,06 7,00 0,63 Rivera B 2,79 54,0 24,0 0,35 1,77 7,00 0,63 B 5,58 42,0 27,0 0,35 3,54 7,00 0,63 B 3,64 56,0 33,0 0,35 2,31 7,00 0,63 Santa Rosa de Cabal B 3,35 58,0 33,0 0,35 2,12 7,00 0,63 Santa Rosa de Cabal B 1,49 89,0 33,0 0,35 0,95 7,00 0,63 B 10,2 33,2 25,0 0,35 6,47 7,00 0,63 B 3,16 59,5 33,0 0,35 2,00 7,00 0,63 La Cruz (Tajumbina) B 2,79 63,0 33,0 0,35 1,77 7,00 0,63 Tibirita B 8,12 43,3 33,0 0,35 5,15 7,00 0,63 Tibirita B 4,70 50,8 33,0 0,35 2,98 7,00 0,63 B 10,7 33,8 26,0 0,35 6,80 7,00 0,63 Utica B 16,7 31,0 26,0 0,35 10,61 7,00 0,63 Villamaría B 2,79 63,0 33,0 0,35 1,77 7,00 0,63

TOTAL 272 14,4 173 287

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CERRO BRAVO showing a semblance with the springs from Santa Rosa El Jordán 6,7 4,5 sector in the group 6, which lead to a high reservoir Aguacatal 3 1,2 temperature. Considering the temperature and composition 1050000 10 1 La Calera of these bicarbonate waters they are not form in the 11,12 8.9 6.7 Hotel San Luis periphery of the system but close to the upflow zone. The Santo 7 Termales Domingo 1,2 4 Botero 8 absence of chloride water on surface could be explained by 52,3 4 Aguas 1040000 1 Londoño 56 9 103 Calientes the mixing of the deep hot chloride fluid with steam heated 5 1,4,5, NEVADO DEL 2 15 11 RUIZ 8 10 3 6,7 water at shallower depth. Such a mixing at short distance 9Cristalina 2Nereidas Gualí El 9 Alta y baja 12 1 10 Calvario from Cerro Machín volcano would lead to the conclusion of 3,4 1030000 14 9 Chorro 2 6,7,11 4 8 - El 13 65 Negro 14 El Oso 2 a hydrothermal system of small dimensions as it was 10 Recodo 1,15 13 Quebrada Santa 8 Hacienda 12 San Vicente y Corralitos formulated before from geovolcanological and tectonic Rosa Granates El Cortijo 3 criteria (CHEC et al., 1983). The reservoir temperature was 1020000 1 3,4 estimated in 220-240°C from the Na/K geothermometer and 7 La Yuca El Bosque NEVADO DEL TOLIMA in 200°C from the quartz geothermometer. del Otún 9 1010000 10-14 Romerales El 16 Enthalpy of saturated steam at 100°C 7,8 Cebollar Aquilino 13 2500 El 3 15 Rancho 8 2 5,6,7 2250 1000000 1 4 (El Turpial) 2000 MACHIN Río 8 Toche 136 4 12 990000 5,9 1750 7,11 9 23 1 14,17 16 10 Puente 1500 Tierra 15 Geothermal reservoir water La Piscina (Q. Aguas Calientes) 1250 id lu r f 840000 850000 860000 870000 880000 oi rv se

Enthalpy (kJ/kg) re 1000 e Figure 2. Location of groups of hot springs from the th om fr 3 9 n 1 2 4 Cerro Bravo – Cerro Machín Volcanic Complex. 750 tio 15 Boiling process ilu d 11 ct 6 7 Chloride springs are represented by red, ire D bicarbonate springs by blue and sulphate by 500 ng r boili green. Discharge temperature below 40°C n afte 250 Dilutio correspond to empty circles, between 40 to 60°C 10 1314812 5 to half filled circles and higher than 60 °C to 0 filled circles. 0 100 200 300 400 500 600 700 800 900 Chloride (mg/l) (91°C) is found at chloride springs from San Vicente with Figure 3. Enthalpy – Chloride model (Arnórsson, 2000). chloride concentration up to about 886 mg/l, lithium up to The composition of bicarbonate springs from 5.6 mg/l, boron up to 22.7 mg/l with relatively low Santa Rosa with a relatively low discharge bicarbonate and sulfate (275 and 30 mg/l, respectively). The temperature and the highest silica contents, are Na/K geothermometer indicates a reservoir temperature explain from this model, as the dilution directly around 280°C. Bicarbonate springs from the Santa Rosa from the reservoir water at about 310°C. Hotter sector with discharge temperatures between 50 to 65°C, springs from San Vicente seem to be the result of register the highest silica contents, from which temperatures boiling and subsequent dilution. around 200°C are inferred. To explain this behavior the Enthalpy-chloride model presented in Fig. 3, was applied. As conclusion, the geothermal system of Santa Rosa de Two processes clearly identified are postulated to explain Cabal could be independent from Nevado del Ruiz system as the differences in composition and particularly in silica the geochemical temperatures suggest. Santa Rosa would be contents of the springs from the two sectors: (1) direct a higher temperature system which heat source could be mixing from the hot reservoir geothermal fluid with low associated to the magmatic bodies of Paramillo de Santa temperature shallow water to form the springs of Santa Rosa Rosa but nor necessarily related to eruption events which and (2) Boiling of the geothermal fluid and thereafter, last occurrence was estimated as too old to be considered as mixing with low temperature shallow water, to form the a good heat source (CHEC et al., 1983). Taking into springs from San Vicente. So, at Santa Rosa springs, the account the very high estimated reservoir temperature at mixing with shallow water decrease the chloride and silica Santa Rosa area, and the favorable permeability conditions contents and increase bicarbonate (and also and inferred from geological contacts (andesitic and the ) while in springs from San Vicente, the boiled fluid Quebrada Grande Formation), from several faults like San which gives place to the formation of the springs, has a Ramón, Campoalegrito, San Eugenio, La Cristalina crossed lower temperature than the reservoir (that is lower silica perpendicularly by Laguna Baja, which is a normal fault contents) and higher chloride concentration, resulting from (CHEC et al., 1983) and, from the occurrence of numerous the boiling process. From the Entalphy – Chloride model, hot springs. the reservoir temperature extrapolated from the dilution trend of Santa Rosa sector springs would be around 310°C. 3.1.2 Cundinamarca Department Cundinamarca Department, located in the central region of The group 9, located at the south of the area near to the Colombia on the Eastern Cordillera in a sedimentary Cerro Bravo Machín volcano, is formed by 17 bicarbonate geological setting and with an approximate area of 22.600 springs, located along the Toche River and bordering areas km2 has at least 42 thermal springs well spread out from to the of the volcano. Warm and hot springs from west to east. They reflect the existence of low temperature this group show a relatively high chloride, lithium and systems, in the main, likely related to the normal geothermal boron, which in the hottest spring (94°C) get 300 mg/l, 2.7 gradient as heat source. The highest temperature resources mg/l and 15 mg/l, respectively. Besides this, these springs inferred from the springs are located towards the east at exhibit high silica contents (of the order of 300 mg/l) Gachetá, Tibirita and Paratebueno municipalities, where 4 Alfaro et al. mesothermal geothermal gradients (50-60°C/km) were deposits (ash and flows), pyroclastic surge and one estimated. Their isotopic composition reveals two probable debris flow () deposit, is found from the north to the processes affecting the springs; one in springs from Útica south-east, reaching Sapuyes river, and to the west sector in municipality, which shows an enrichment likely due to the basin of the Guisa river. El Carrizo Member, made of evaporation as their high salinity suggest and, in the springs ash and blocks flow deposits is located in a limited area to from the plateau named Sabana de Bogotá, which show a the south-east of the volcano following the margins of the lighter stable isotopic composition with respect to the creeks . El Carmelo and El Carrizo. Finally, springs from both sides of the plateau. This reveals the Member, located in the closest to the volcano areas, consists contribution of different processes in the formation of the of deposits of pyroclastic surge related to the most recent precipitation water. A more complete description of the activity of Azufral volcano (Torres, et al., 2003). results of this spring inventory is presented in a separated paper in the frame of this congress (Alfaro, 2005). 3.2.1.2 Hot Springs Geochemistry The chemical composition of the hot springs, updated during 3.2 First Stage of Exploration 2002, did not show major variations with respect to 3.2.1 Azufral volcano measurements done 17 and 22 years ago (Olade, et al. 1982 and Olade, et al., 1987) which interpretation was briefly Azufral volcano is a strato-volcano located on the Cordillera described in the proceedings of the last world geothermal Occidental, in Colombia, which priority as a geothermal Congress (Alfaro et al., 2000). The general features of the prospect is well known and was registered in the frame of eight sampled springs include neutral pH for all of them, the previous world congress (Alfaro, et al, 2000). The discharge temperatures between 18 and 49°, high salinity geological cartography of the area in a scale 1:25.000 was which source presumably is not the geothermal fluid as low studied by INGEOMINAS (Torres & Bernal, 2002). It temperature springs shows high salinity and a variable included the compilation and interpretation of the geology of 2 contribution from that saline source to the springs. From the some surrounding areas to cover a total area of 1400 km . discharge temperature (47.3 °C), total dissolved solids (2036 mg/l) and the relative Cl-SO4-HCO3 illustrated in the Fig. 4 3.2.1.1 Geological Setting and the Cl-HCO3-B compositions the Quebrada Blanca hot The outcrops of the area consist of metasedimentary rocks of spring seems to receive the major contribution of the Dagua Complex of Lower to Upper Cretaceous geothermal fluid. age and volcanic-sedimentary rocks from the Diabasic Complex, in the main. These shaped by the basement and The aqueous geothermometers applied to the hottest, are intruded by porfiritic rocks of andesitic to quartz-dioritic chloride springs (Quebrada Blanca) and mixed chloride- composition, which Paleogenic ages are between to bicarbonate springs (Tercán I and II, also know as Quebrada Later and from which the intrusive body of El Baño), which besides the spring of Laguna Verde, are Piedrancha stands out. From the Upper Miocene the also the closest springs to the crater, point out high sedimentary Formation of Esmita is registered, conformed temperatures (above 215°C for Na/K geothermometer, by green fossilipherous limolites, narrow carbon lens in the above 178°C for the quartz geothermometer). However, the middle of the sequence and polymictic conglomerates with discharge water of these springs does not represent the ratio intercalations of in the upper part (Torres & of the alkaline ionic species in the reservoir as a high sodium Bernal, 2002). The volcanic rocks from the Neogene consist contribution is registered from a non geothermal source and of andesitic, dacites and rhyolites discordantly deposited on from this, the estimated temperatures would not be reliable. the previous geological strata. On the other hand, the high dilution and possibly even a The stratigraphy of the recent volcanic deposits supported by conductive cooling affects the quartz geothermometer, as the a geochronological study (14C), was the basis for the Enthalpy – Silica model from the Fig. 5 shows. That is, the definition of the geological formation of Azufral (Torres, et reservoir temperature should be above 178°C and a more al., 2003) which covers an area of 420 km2 and have a precise estimation from surface, requires the application of thickness is about 80 m thick. It consists of rocks and other geothermometers such as those based on gases deposits resulting from the explosive volcanic activity of composition. Azufral volcano, registered from 17.790 ± 90 to 3370 ± 70 Cl 1 0 years BP. Typical columns of Azufral Formation are located 0 0 at the Sabana de Túquerres, east flank of the volcano, as well as in the basins of Azufral, Pacual, Sapuyes, Verde and

7 Guisa rivers. 5 5 2 MATURE Azufral Formation is divided, from bottom to top, in six (6) WATERS S R E T members: The Túquerres Member consists of deposits of A Quebrada Blanca W 5 0 0 surge and , which can be found at the east 5

Tenguetán

and south east of the volcano and, debris avalanche deposits TercánMalaver 21 IC N found at the south. La Calera Member conformed by an ash A P C E L R I O San RamónP and blocks pyroclastic flow, ash and pumice and by deposits V H 2 5 E 5 7 R A of pyroclastic surge, which highest thickness outcrops L

W A T mainly at the west and south-west while towards the south, E R east, north and north-east it has lower thickness. The Laguna Verde 0 0 0 STEAM HEATED WATERS La Cabaña Cortadera Member has interlayered ash flow and pumice 1 - = HCO deposits with pyroclastic surge deposits and is widely SO 3 4 0 255075100 distributed around the volcano. It is found in very close to Figure 4. Relative Cl-SO4-HCO3 composition for springs the crater area as well as in distant places: Planada de of Azufral volcano (Base diagram from Chapuesquer to the north, La Oscurana, to the west and El Giggenbach, 1991) Quebrada Blanca spring has Tambillo at the south-west in the proximity of Cumbal the highest mature water contribution. volcano. El Espino Member, which consists of pyroclastic

5 Alfaro et al.

700 movements during the uplift. These displacements in the 650 Eastern Cordillera (transpression) from Pliocene, have been

600 considered by De Freitas et al (1997), Kammer (1999),

550 Taboada et al (2000), Sarmiento (2001) and Acosta (2002). This lateral movement affects even the inverted structures in 500 Qtz solubility curve the axial zone of the mountain chain, where the cordillera for maximun steam loss 450 shows symmetry. 400 Enthalpy of boiling Qtz solubility Curve (mg/l) 350 water at 100°C The regional interpretation of Landsat Images allows the 2 300 recognition of NEE linear features related to the traces of SiO

250 Boyaca, Soapaga and other faults (longitudinal faults), as Tercán springs Laguna Verde well as the identification of geomorphic features related to 200 Quebrada Blanca Malaver wrenching or lateral movement additional to the vertical 150 San Ramón Tenguetán displacement of the faults (Velandia, 2003). The identified 100 La Cabaña regional faults are interpreted as an imbricate fan by 50 overlapping fault propagation to the SE with some strike slip 0 motion as is suggested by the oblique arrangement of fold

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 axes regarding the main fault traces. In addition to the 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 1 1 1 1 1 1 1 longitudinal faults (NEE), a transverse array is also Enthalpy (kJ/kg) identified in the area, which is related to the basement faults Figure 6. Stable isotope composition of springs from that probably controlled the cretaceous sedimentation and Azufral Volcano. A slight oxygen enrichment if even the presence of the Neogene-Quaternary volcanic found at the hottest springs (Quebrada Blanca, deposits in the Paipa area, suggesting an extensional Tercán) character of these NW faults. The obtained geological map of the Paipa geothermal area 3.2.2.1 Tectonic Frame (Fig. 7) in 25:000 presents an updating and detail of the During Late Miocene and Pliocene a fold and thrust belt was structural knowledge to better explain the geothermal generated in the Eastern Cordillera, followed by the regional system. This is also based on previous regional geological raising of the whole chain in the Pliocene-Pleistocene mapping (Renzoni & Rosas, 1983) and studies about (Dengo and Covey, 1993). These authors suggest that the geothermal and volcanic aspects (Ferreira & Hernández, raising occur along thrust and back-thrust faults with the 1988 and Hernández & Osorio, 1990). The area is detachment in the cretaceous sedimentary and incompetent dominated by Cretaceous marine sedimentary rocks and units, and along normal basement faults reactivated as Late Cretaceous to Paleogene continental sedimentary rocks, reverse and thrust ones during the Mesozoic, as the Boyaca as well as Neogene to Quaternary unconsolidated deposits, Fault. This tectonic inversion in the Eastern Cordillera has being important the volcanic and volcanoclastic deposits and been documented by authors like Fabre (1983), Colletta et al a local hydrothermal breccia that can be related to a (1990), Dengo & Covey (1993), Cooper et al (1995), magmatic heat source for the geothermal system although they no not mention the occurrence of strike slip

Figure 7. Geological Map of the Paipa Geothermal Area. Location of structural cross sections A-A’ and B-B’ presented in Figure 8 are indicated here.

6 Alfaro et al.

.

Figure 8. Structural cross sections A-A’ and B-B’ (located in geological map – Fig. 7), showing detachment level under Plaeners Formation and basement faults related to the volcanism and the upflow of the geothermal fluids

3.2.2.2 NEE Longitudinal Faults 3.2.2.4 NE Transverse Faults Geological mapping and seismic interpretation carried out in These faults affect the sedimentary sequence and the area, allowed to obtain a structural scheme, where NEE microtectonic data were obtained in some of them, oriented faults are outlined with a parallel orientation to the indicating right lateral displacements. El Hornito and main faults in the region, as Soapaga and Boyaca. The Canocas faults concern the longitudinal structures and are interpreted geological cross sections (Fig. 8) are showing interpreted as tear structures associated to thrusting. Also, two structural styles: - one that affects the basement and these structures are considered as the most recent result of considered as thick skin, which also cuts the cover sequence faulting in the area. The Santa Rita Fault is interpreted as a and - other with thrust faults that are restricted to the lateral ramp of El Batan . sedimentary rocks of the cover and known as thin skin. 3.2.2.5 Structural Geology Discussion The thick skinned style would be related to the reverse Lanceros Fault, that has an opposite dip with regard to the In general, the obtained model shows structures that can be Soapaga Fault, between which a block would be expelled in interpreted as a product of the reactivation of previous the shape of "pop-up". The thin skinned style is associated to structures and the generation of new faults under the Andean the El Bizcocho and El Batan thrust faults, where the last compressive regime, which shows transpressive one represents the front or more distal fault of the features in the area by the effect of a NW-SE oriented overlapped fan that is verging to the SE from the Boyaca maximum horizontal stress, assumed under an approximated Fault, with detachment along the Plaeners Formation bottom regional tensor of 122° (from Taboada et al, 2000 and Toro, (Fig. 8). 2003). This transpression causes thrusting, normal to the tensor 3.2.2.3 NW Transverse Faults orientation and lateral displacements along oblique faults to These structures are observed especially to the South of the this orientation due to the local partitioning. Longitudinal area. The Cerro Plateado Fault is observed as a shear zone in and transverse faults shape blocks that can acquire an the hill, it consists of the Formation sandstones (Fig. 7) independent movement, including rotation, under this and with a trace along the Honda Grande creek valley to the partitioning. This kinematics is shown in Fig. 9, and allows NW that separates the volcanic bodies that usually have proposing an application of the structural interpretation to been known as Olitas on the south and Pan de Azucar to the the exploration of geothermal resources. north. The Los Volcanes Fault crosses the hill of the same name, where the Olitas volcanic deposit is located; From the structural model and location of current hot regionally its trace continues to the SE up to another springs, some promissory zones are proposed for future volcanic body and geothermal system known as Iza. These exploration (Fig. 9). These are related to: - The fault traces, two faults are interpreted as basement structures related to a especially along the NE and NW transverse ones, since they previous extensional tectonic phase, which was reactivated can allow the flow of fluids, and along some NNE during Andean uplift, preserving the character of open longitudinal faults; - The crossing of longitudinal and breaks that facilitate the hydrothermal fluid flow; they are transverse faults, since it is assumed that the connection with even assumed as faults of such depth that allow the ascent of the heat source happens especially along NW transverse and the volcanism in the area faults and of some longitudinal faults as the Agua Tibia

7 Alfaro et al.

Fault; - Corners opened by the rotation of blocks between the caldera, with eruptive foci towards the southeast rim, the El Hornito, Canocas and Santa Rita faults, since the right that is in the sector of the head board of the Olitas creek. The lateral movement generates a distension in the surrounding main feature of this epoch is the domes production which of the cross of tear faults (NE) and NEE longitudinal faults, collapse generated pyroclastic flows that remained confined which are displeased. to the caldera depression.

The relation between the hydrothermal and the volcanic- magmatic systems can be derived from the following observations: (1) the surface manifestations (hot springs and steaming ground) discharging abundant CO2, are located inside and toward the rim of the inferred volcanic area. (2) There is a magmatic camera likely located under the caldera structure, in the metamorphic rocks, which constitute the core of the Cordillera, that would be the heat source of the hydrotermal system. (3) There are alteration minerals at the focus of the two identified eruptive events which are indicative of existence of hydrothermal fluids.

3.2.2.7 Geochemistry of the Hot Springs The geochemistry of the aqueous phase of springs from Paipa geothermal area, was interpreted by Alfaro & Pang (2003) as follows: The hot springs from Paipa geothermal area aligned along about 7 km (Fig. 10). Two main sectors: ITP-Lanceros, La Playa host most of the springs. Two isolated low temperature springs are registered in the sectors identified as El Hervidero, which main feature is the permanent and abundant CO discharge, and Olitas. Figure 9. Structural model for the Paipa Geothermal 2 Additionally, there are two shallow wells of warm water Area showing the proposed promissory zones for (21°C) which feed the industrial plant of sodium sulphate future exploration. Movement direction (thick (SALPA) and were including in the sampling. The black arrows) of the shear zone causes thrusting, temperature reaches 76°C in the spring number 1 from La relative displacements and blocks rotation (red Playa Sector. The highest salinity is found at the shallow arrows), as well as open zones along parallel fault wells (21 and 22). traces, where strike-slip also occurs. This

kinematics is considered to point out certain MPP02 sectors as geothermal promissory areas.

1138000 3.2.2.6 Vulcanology 19 The outcrops of volcanic rocks in the municipalities of 1136000 Paipa, Tuta and Iza have been considered anomalous in the MPP05 frame of the sedimentary geology of the Cordillera Oriental. 1134000 18 The volcanic products cover an elongated area of about 31 2 17 km , in NE direction, between the municipalities of Paipa 1132000 26 PAIPA and Tuta. Following lithological, geomorphological and structural factors the area can be divided in the sectors: El 1130000 SALPA Guarruz, to the north east and, Olitas to the south west. 2122 MPP04 23 ITP - LANCEROS 14C14A14B138 From the lithology and the rocks distritution, the focus of the 7,8,9,10,11 1128000 12,13,14,20 volcanic rocks is at Olitas sector. This lithology is 24 dominated by pyroclastites interlayed with sedimentites 1126000 from fluvial, colluvial and lacustrine, environments, domes 5 1 6 and volcanic lavas. The pyroclastic flows are more abundant LA PLAYA MPP01 than the pyroclastic fall deposits. The sedimentites are 1124000 16 dominated by the sand and slime granulometry. The EL HERVIDERO 25 tephrastratigraphy shows that the volcanic rocks overlay 1122000 MPP0315 discordantly the sedimentary rocks from the Cretaceous and PISCINA OLITAS the current soil was developed on them, except in some 1102000 1104000 1106000 1108000 1110000 1112000 1114000 1116000 valleys where fluvial and colluvial sediments overlay the vulcanites. Figure 10. Location of springs and precipitation water samplers at Paipa geothermal area.

From more than 20 stratigraphic columns of the volcanic The predominant dissolved species in the high salinity warm area a general stratigraphic column was obtained in order to and hot water samples from the geothermal area of Paipa, track the eruptive activity. Two main eruptive epochs were are sodium and sulfate as the Shoeller diagram (Fig. 11) Identified: The first one is represented by explosive indicates. eruptions that produced pyroclastic flows by the column collapse. This epoch seems to have finished with a collapse, which gave place to the formation of a 3 km diameter caldera with a rough depth of 400 m. The second epoch could be interpreted as a resurgence of the first one, inside 8 Alfaro et al.

1000 21 loss before mixing and quartz as the mineral controlling the ITP-Lanceros, La Playa sectors silica solubility

100 Na/10001 0 0 0

24

23 10 7 5 5 2

Equilibrium Line IZ01 140° 1 160° 1 ° 2 180 0 ° ° 5 0 00 0 26 5 2 1

Concentration (meq/l) Concentration 0 ° 0 0 ° 2122 PP7,8,9, 0° 8 4 710 0 2 128 10,11,13 ° ° 922 IZ02 0 1120 6 Partial Equilibrium 2 14B ° 0 25 8 0 2 1 ° 0 14A 0 3 ° 14C 2 0 13 IZ03 5 2 5 7 °3 0 4 15 3

IZ-02IZ-01 0 IZ-0324 0 15 2623 Na Mg HCO 0 K CaCl SO 0 Immature water 25 4 3 1 Major dissolved species 0.5 K/100 Mg 0 25 50 75 100 Figure 11. Schoeller diagram for Paipa and Iza springs (Base diagram from Schoeller, 1955). A Figure 12. Relative Na-K-Mg at springs from Paipa predominance of sodium and sulphate is clearly (Base diagram from Giggenbach, 1988). A clear observed. The highest sodium sulphate contents is mixing trend includes high salinity water and hot found at a shallow low temperature water (point springs. 21). Although the quartz geothermometer is relatively low, its From the X-ray characterization Sodium sulphate is also the presence in the reservoir was assumed from the results of the composition of the efflorescent white salt and the crusty application of the code SOLVEQ. For Iza springs the white deposit, found on surface wide spread out in the hot highest estimate temperature by applying the enthalpy silica springs area in the form of mirabilite (Na2SO4.10H2O) and model is 260°C. thenardite (Na2SO4). The saline source controls also the conservative species as lithium and boron. The only species The stable isotopes composition presented in the Fig. 13 which seems to follow a correlation with temperature is shows an isotope enrichment particularly of oxygen-18, fluoride, which gets a highest concentration of 18-20 mg/l at which reaches its higher magnitude (around 4 ‰) at the La Playa, the hottest sector. Hot springs from Iza, a warm water shallow wells from SALPA with the highest separated geothermal system located about 15 km south observed total dissolved solid contents and identified as from Paipa, which occur in a similar geological setting but highest sodium concentration in the mixing line observed in without the influence of such a saline source, was included the Na-K-Mg relative composition diagram. The warm and as a reference. They are identified as IZ#. As it would be hot springs follow about the same linear trend defining a line expected, the hot springs from Paipa as mostly sulfate while with a slope of 1.4. On the other hand, the sample PP16 (El Hervidero), shows a high δ8O depletion (around 5.5 ‰) the springs from Iza are chloride and bicarbonate with 18 evidence of high dilution. probably due to the O exchange between CO2 and H2O, as it was explained before by Bertrami, et al., (1992). Their relative Na-K-Mg composition dominated by sodium shows a clear mixing trend (Fig. 12) from which more The oxygen-18 enrichment could be due at least to three concentrated end-members are the warm shallow waters processes: Evaporation (suggested by Bertrami et al., 1992), from SALPA . The hot springs of are aligned along the high temperature water-rock interaction and, percolation mixing trend which cannot be extrapolated on the through evaporitic hydrated minerals isotopically enriched equilibrium line as the chemical composition is influenced from a sedimentary basin. The evaporation process would by the shallow saline source and do not represent the deep not be rare as the precipitation of the area is lower than the fluid. On the other hand the springs from Iza highly diluted evaporation. However, the expected slope for dry conditions would be between 2.5 and 4 (Sofer, 1978). The possible high with cold ground water as their relative magnesium 18 concentration indicates, point out a temperature between 240 temperature water-rock interaction reflected in an O to 260°C by extrapolation on the equilibrium line. enrichment could not be distinguished in the hot springs, as the end member of the mixing is a shallow high salinity low Since alkaline geothermometer cannot be reliable, silica temperature water. Thus, the percolation through hydrated geothermometers were applied to estimate minimum minerals and the oxygen-18 exchange is likely one or the reservoir temperature which highest values indicate 120°C process controlling the isotopes enrichment. This is common for quartz and 95°C for chalcedony. The highest silica process in sedimentary basins and could happen at Paipa concentration was found at Olitas spring (167 mg/l) which geothermal area which is related to the Chicamocha river does not seem to be consistent with it low temperature basin. From this, the hydrated minerals are part of a non- (23°C). According to the Enthalpy – silica model this marine evaporitic deposit, which are also the source of concentration seems to be controlled by the amorphous silica sulphate and sodium to form thenardite and mirabilite on and explained by the infiltration of meteoric water through surface. high silica rocks as the rhyolitic volcanic deposits and possibly, the subsequent slow uprising flow with conductive cooling without silica precipitation. From the same mixing model the highest temperature of 230°C is estimated assuming dilution of geothermal fluid without steam or heat

9 Alfaro et al.

-35.0 Valley, Colombia. PhD. Thesis. Imperial College. -40.0 13 8. London. 8 + -40.0 -50.0 MPP03MPP04 1 Ο δ MPP05 ∗ 63 MPP01 . 7 Alfaro, C., Bernal, N-. Ramírez, G., Escovar, R. 2000. Colombia, -60.0 PP16 = 2 Η -45.0 [o/oo)D V-SMOW PP-06 : MPP02 PP19 PP-07

δ δ e PP-12PP-09PP-04 Country Update. In: Iglesias, E., Blackwell, D., Hunt, T., PP11 PP23PP-01 PP20 in PP-10PP-08 PP21 L -70.0 ic PP-05 PP22 r 0 PP18PP17PP-14-APP-14-B o 1 PP25PP-14-CPP-13 e + Lund, J, and Tamanyu, S. (Editors) Proceedings. World PP26 t 8 PP15PP24 e 1 Ο M MPP03MPP04 l δ -50.0 ba ∗ Geothermal Congress 2000. Digital format. Paper 512. -80.0 lo 8 G = -16.0 -14.0 -12.0 -10.0 -8.0 -6.0 2 Η 18 δ O [o/oo] V-SMOW δ 10 pp MPP05 -55.0 Y = 7.04606 * X + 5.56629 R = 0.993 MPP01 Alfaro, C., Aguirre, A. and Jaramillo, L. F. 2002. Inventario de -60.0 fuentes termales en el Parque Nacional Natural de los 6 19 Y = 1.37576 * X + -58.3197 Nevados. INGEOMINAS. Technical report. Bogotá. 101 R = 0.8785 D [o/oo) V-SMOW D [o/oo) -65.0 MPP02 7 pp δ 12 4 11 9 23 1 20 10 8 21 -70.0 18 17 Alfaro, C. & Pang, Z. 2003. Preliminar geochemistry of the Paipa 25 5 22 26 14A 14B 1314C Geothermal system, Colombia. Submitted to -75.0 15 24 Geothermics.

-80.0 Alfaro, C. 2005. Geochemistry of hot springs at Cundinamarca Department, Colombia. Paper 0831. Proceedings of the -11.0 -10.0 -9.0 -8.0 -7.0 -6.0 18 World Geothermal Congress 2005. Antalya, Turkey, 24- δ O [o/oo] V-SMOW 29 April 2005.

Arnórsson, S. (Ed). 2000. Isotopic and chemical techniques in geothermal exploration development and use. Sampling Figure 13. Stable isotopes compositions of springs from methods, data handling, interpretation. IAEA. Vienna. Paipa. The high enrichment observed at the 351 pp. shallow low temperature water of highest salinity Bertrami, R., Camacho, A., De Stefanis, L., Medina, T., and Zuppi, (21) suggest its relation with evaporitic minerals. G., 1992. Geochemical and isotopic exploration of the The d18O depletion (around 5.5 ‰) at El 18 geothermal area of Paipa, Cordillera Central, Colombia. Hervidero (PP16) is probably due to the O Geothermal investigations with isotope and geochemical exchange between CO2 and H2O. techniques in Latin America. IAEA. Proceedings of a Final Research Co-ordination Meeting held in San Jose, As the hot springs do not keep the isotopic composition of Costa Rica, 12-16 November. 1990. pp 169-199 the reservoir, their recharge elevation could not be determined. Hot springs from Iza are isotopically lighter and Calvache, M. & Monsalve, M.L. 1982. Geología, Petrografía y based on the correlation found with precipitation water from Análisis de Xenolitos en el Área A (Zona de Manizales) the area of Paipa, their recharge elevation is between 3200 del Proyecto Geotérmico en la Región del Macizo Volcánico del Ruiz. Universidad Nacional de Colombia. and 3500 m.a.s.l. Departamento de Geociencias. Tesis de Grado. Central Hidroeléctrica de Caldas (CHEC). Sección Geotermia. In conclusion, the geochemistry of the springs related to the Manizales,118 p. geothermal system of Paipa is complex due to a mixing Central Hidroeléctrica de Caldas (CHEC), Instituto Colombiano de process, occurring nearby the surface, of deep geothermal Energía Eléctrica (ICEL), Consultoría Técnica water with shallow sodium sulfate water, enriched in 18O Colombiana Ltda. (CONTECOL) and Geotérmica and 2H. The reservoir temperature could reach up to Italiana. 1983. Investigación Geotérmica. Macizo 230°C. From this, Paipa is a high temperature geothermal volcánico del Ruiz. Fase II, Etapa A. Vol. I, II, III and system. This type of systems and the permanent and IV. Bogotá. Colletta, B., Hebrard, F., Letouzey, J., Werner, P., Rudkiewicz, J. abundant discharge in springs and wells are 1990. Tectonic style and crustal structure of the Eastern consistent with the magmatic heat source. The high Cordillera (Colombia) from a balanced cross-section. In discharge of carbon dioxide could be related to the found Letouzey, J., ed., Petroleum and tectonics in mobile correlation between fluoride and temperature (silica belts: Paris, Editions Technip, p. 81-100. contents). The fluoride would be in solution as a result of the Cooper, M., Addison, F., Alvarez, R., Coral, M., Graham, R., calcium precipitation as calcite deposits. The springs from Hayward, A., Howe, S., Martínez, J., Naar, J., Peñas, R., the south (El Hervidero (PP16) and Piscina Olitas (PP15)) Pulham, J., Taborda, A. 1995. Basin development and are not affected by the high salinity ground waters and seem tectonic history of the , Eastern Cordillera, to belong to separated hydrological circuits. and , Colombia. AAPG Bulletin, Vol. 79, No. 10: 1421-1443. ACKNOWLEDGMENT Dengo, C., Covey, M. 1993. Structure of the Eastern Cordillera of The authors are grateful to the International Atomic Energy Colombia: implications for trap styles and regional Agency. Through the cooperation project COL/8/022 was tectonics. AAPG Bulletin, Vol. 77, No. 8: 1315-1337. possible to obtain all the presented isotopic analysis included in this work. Special gratitude is express to Fabre, A. 1983. La subsidencia de la Cuenca del Cocuy (Cordillera Zhonghe Pang from the IAEA for his permanent support. Oriental de Colombia) durante el Cretáceo y el Terciario. Segunda Parte: Esquema de evolución tectónica. Revista Thanks also to our colleagues from the geothermal Norandina, No. 8: 21-27. Bogotá. exploration project, the geology section, the geophysics Ferreira, P., Hernández, R., 1988. Evaluación geotérmica en el área section and from the Water and Gas Laboratory. Their de Paipa, basada en técnicas isotópicas, geoquímica y contributions allowed to develop the work presented here. aspectos estructurales. Tesis de grado. Universidad Nacional de Colombia, Departamento de Geociencias. REFERENCES 125 . Acosta, J., 2002, Structure, tectonics and 3D models of the western Freitas de M., Froncolin, J., Cobbold, P., 1997. The Structure of the foothills of the Eastern Cordillera and Middle Magdalena axial zone of the Cordillera Oriental, Colombia. VI

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Simposio Bolivariano “Exploración petrolera en las Renzoni, G., Rosas, H., 1983. Mapa Geológico Plancha 171- cuencas ubandinas”. Memorias. Tomo II: 38-41. . Escala 1:100.000. INGEOMINAS. Bogotá. Cartagena. Sarmiento, L., 2001. Mesozoic rifting and cenozoic basin inversion Giggenbach, W. F., 1988. Geothermal solute equilibria. Derivation history of the Eastern Cordillera, Colombian . of Na-K-Mg-Ca geoindicators. Geochim. Cosmochim. Inferences from tectonic models. PhD. Thesis. Vrije Acta, 52: 2749-2765. Universiteit Amsterdam. 296 p. Schoeller H (1955) Géochemie des eaux souterraines. Rev Inst Fr Giggenbach W. F. 1991. Chemical Techniches in geothermal Pétrol 10:230–244 exploration. En: D’Amore, F. Application of Geochemistry in Geothermal Reservoir Development. Sofer, Z. 1978. Isotopic composition of hydration water in gypsum. Rome. pp 119-142 Geochímica et Cosmochímica Acta, Vol. 42. pp 1141 to 1149. Geocónsul S.A. de C.V. 1992. Evaluación Geotérmica del Macizo Volcánico del Ruiz. Informe Final. Preparado para Taboada, A., Rivera, L., Fuenzalida, A., Cisternas, A., Philip, H., Constructora y Perforadora Latina, S.A. de C.V. Morelia Bijwaard, H., Olaya, J., Rivera, C., 2000. Geodynamics (Mexico). 57p. of the northern Andes: and Intracontinental deformation (Colombia). Tectonics, 19 (5): 787-813. Hernández, G., Osorio, O., 1990. Geología, análisis petrográfico y químico de las rocas volcánicas del suroriente de Paipa Toro, A., 2003. Determinación de los tensores de esfuerzos actuales (Boyacá-Colombia). Tesis de grado. Universidad para diferentes regiones del territorio colombiano Nacional de Colombia. Bogotá. calculadas a partir de mecanismos focales de sismos mayores. Tesis. Universidad de Caldas. Manizales. Kammer, A., 1999. Observaciones acerca de un origen transpresivo de la Cordillera Oriental. Geología Colombiana, 24: 29- Torres, P., Bernal, N. 2002. Cartografía geológica del volcán 53. Bogotá. Azufral de Túquerres, Nariño. V 1.0. Memoria Explicativa. INGEOMINAS. 14 pp Nicholson, K. 1993. Geothermal Fluids. Chemistry and Exploration Techniques. Spring Verlag. Germany. 263 pp. Torres, M. P., Calvache, M. L., Cortés, G. P. and Monsalve, M.L. 2003. Propuesta estratigráfica para la definición formal Organización Latino Americana de Energía (OLADE), ICEL, de la formación Azufral, Colombia. In: Toro, G. E.., Geotérmica Italiana S. R. L. and Contecol. 1982. Estudio Weber, M. & Caballero, H. 2003. Resumenes. IX de reconocimiento de los recursos geotérmicos de la Congreso Colombiano de Geología. Medellín, Colombia. República de Colombia. 455 pp 306 pp.

OLADE – Instituto Ecuatoriano de Electrificación (INECEL) - Velandia, F., 2003. Interpretación de transcurrencia de las fallas ICEL. AQUATER, 1987. Proyecto Geotérmico Soapaga y Boyacá a partir de imágenes Landsat TM. IX Binacional Tufiño-Chiles-Cerro Negro. Estudio de Congreso Colombiano de Geología. Medellín. Prefactibilidad. Five volumes.

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